Several mining companies have made large oil and gas investments over the past two years, begging the question: should other globally-diversified miners consider expanding into the sector as well?

Anglo-Australian miner BHP Billiton Ltd. has been at the vanguard of such investment, having plowed about $20 billion into U.S. shale-gas businesses over the past two years. Likewise, India-focused Vedanta Resources PLC has spent $8.7 billion to buy a majority stake in Indian oil and gas explorer Cairn India Ltd.

Meanwhile, other diversified mining companies such as Glencore International PLC and Kazakhmys PLC have invested in oil. Glencore bought a majority stake in Russia’s marine-fuel supplier Chemoil for $237 milllion in 2010 and owns stakes in other oil-producing assets.

Kazakhmys also ventured into oil exploration but exited the business at a loss last year.

But despite the cruelly timed reminder of what might have been if Cairn hadn’t decided to sell down its interest in the firm to Vedanta Resources last year for around $8.5 billion, the company is resolutely locked onto a new course.

However, with its summer exploration campaign offshore Greenland drawing to a close, what it decides to do with the cash soon to be burning a hole in its pocket will be key to its future. Cairn India–spun out of the same Rajasthan assets that transformed the Edinburgh-based explorer’s fortunes overnight when it discovered 3.7 billion barrels of oil equivalent there in 2004–has been relegated to a supporting role in the Cairn Energy story following the divestment, which is still awaiting final government approval .

Although Cairn will retain a 22% stake in the business, it decided to peg its future on one of the biggest–and riskiest–exploration prizes in the world, the huge oil and gas fields reservoirs believed to lurk offshore Greenland.

Zambian copper miners have hit a panic button after the country’s newly elected leader stepped up efforts to deliver on populist campaign promises such as increasing mine taxes and controlling mineral exports.

Veteran politician, Michael Sata, popularly known as King Cobra because of his vicious rhetoric, proved that his bite can be as lethal as his bark after he slapped a ban on copper exports as well as other minerals such as cobalt, gold and nickel this week, in a bid to improve transparency and boost revenue collections.

The development sent shockwaves down the spines of miners such as Vedanta Resources, First Quantum Minerals, and Glencore International. With miners failing to export as much as 2,000 metric tons of copper daily since the ban was announced on Tuesday, the Chamber of Mines, which represents all the operators in the country, sought urgent talks with government.

Instead of settling into the respectable middle tier of global oil producers as its major oil discoveries in Rajasthan, India, gradually come onstream, the U.K.-listed Cairn Energy has decided to do the oil industry equivalent of selling the Volvo, buying a Harley and cruising off into the sunset.

Cairn Energy will sell the bulk of its stake in Cairn India, which owns and operates the Rajasthan fields, to metals and mining company Vedanta Resources. Cairn Chief Executive Sir Bill Gammell leaves behind dreary subjects like pipeline maintenance and enhanced oil recovery and will instead focus his company’s resources on the exciting business of exploring for new fields.

Whether this decision has a happier outcome than the typical mid-life crisis will depend on wildcat drilling in the oil industry’s newest frontier – Greenland.

Cairn Energy PLC

A coastal area of West Greenland, where offshore oil exploration is scheduled to start in July.

If you thought this week was busy, with third quarter earnings coming out of your ears, and GDP figures rocking the market this way and that. Well, you ain’t seen nothing yet.

Next week sees a swathe of big companies reporting as well as a raft of important economic data.

Economic Watch

The Bank of England will decide whether or not to extend its asset purchase scheme. Word on the street is that it will – to around £200billion to £225 billion. Even though the case for doing so looks pretty slim.

Interest rates will also be in focus as the US Federal Reserve and the European Central Bank are set to convene next week. Economists seem to think nothing much will change given the continuing severity of the recession and worrying unemployment rates.

Reporting season continues

There’s a list of companies longer than my arm reporting next week. Biggies to watch out for are Associated British Foods, Metro and UBS on Tuesday. Then there’s Cobham, Marks & Spencer and Taylor Wimpey on Wednesday. On Thursday, ones to watch include Vedanta Resources, Unilever, EasyJet and Cable & Wireless. And the week ends with numbers from British Airways, Smith & Nephew and Tate & Lyle.